1. Field of the Invention
The present invention relates to an internal combustion engine with auxiliary combustion chamber that has a main combustion chamber and an auxiliary combustion chamber smaller than the main combustion chamber.
2. Description of Related Art
Spark-ignition internal combustion engines that improve heat efficiency by lean burn are known. However, lean bum degrades the stability of combustion. In view of this problem, a related art internal combustion engine includes a main combustion chamber serving as a main combustion chamber, an auxiliary combustion chamber smaller in capacity than the main combustion chamber, an injection hole by which the main and auxiliary combustion chambers communicate, fuel supply devices that supply fuel to the main and auxiliary combustion chambers, and an ignition plug capable of igniting the fuel in the auxiliary combustion chamber. The internal combustion engine ignites the fuel in the auxiliary combustion chamber by the ignition plug, and propels a ejecting torch flame into the main combustion chamber through the injection hole, thereby burning an air-fuel mixture.
The related art internal combustion engine can expand a lean limit but cannot improve heat efficiency sufficiently due to an increase in unburned fuel. This is because under lean burn conditions, torch speed is so high in the vicinity of the injection hole that an air-fuel mixture in the vicinity of the injection hole cannot be burned and consequently unburned fuel is emitted from the vicinity of the injection hole.